|Narrative Type: NTSB FINAL NARRATIVE (6120.4)
|Witnesses observed the float-equipped airplane land on the lake and taxi to the middle where the engine was shut down. Two men were seen exiting the airplane and sitting on the pontoons for about 30 minutes, before going back into the airplane. The airplane then taxied several more times across the lake, consistent with a typical procedure used by float plane pilots to rough up glassy water conditions to enable the airplane to lift off sooner. The airplane then taxied to the south end, turned, and departed to the northeast. The airplane lifted off near the end of the lake and attained an altitude of about 100 feet above the water and clear of trees when the witnesses observed the wings begin to wobble. The airplane rolled hard to the left and collided with the terrain in a nose-down uncontrolled descent consistent with an aerodynamic stall. Some of the witnesses detected no change in the engine sounds and commented that there were no signs of engine problems. An examination of the airframe and engine revealed no anomalies that would have precluded normal operation. The length of the lake traveling from the south end to the northeast end is approximately 5,000 feet.
|Narrative Type: NTSB PRELIMINARY NARRATIVE (6120.19)
|HISTORY OF FLIGHT
On July 24, 2008, about 1515 Pacific daylight time, a float equipped Cessna A185F, N6320N, collided with terrain during takeoff from Lake Nahwatzel near Shelton, Washington. The owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certificated private pilot and one passenger were killed; a post crash fire destroyed the airplane. The cross-country personal flight had a planned destination of Auburn, Washington. Visual meteorological conditions prevailed, and no flight plan had been filed.
Witnesses reported that the airplane landed on the lake, and taxied to the middle of the lake. They observed two males get out of the airplane, sit on the pontoons, and then get back into the airplane about 30 minutes later. They observed the engine start without difficulty, and then saw the airplane taxi across the lake several times. Some thought that the airplane was experiencing difficulty becoming airborne, and that the pilot was trying to rough up the water's surface. It went back to the south end, and then turned and departed to the northeast.
The airplane lifted off near the end of the lake. Witnesses said that the wings wobbled when it reached about 100 feet above the water and clear of the trees when it then rolled hard to the left and descended nose down into the terrain. Some witnesses thought that the pilot cut power prior to the left turn; others detected no change and thought that there were no signs of engine problems.
One witness was a pilot, and was at his residence on the east side of the lake. He reported that during the taxi and takeoff, the engine sounded normal to him. The wind was light. When the airplane passed his range of vision, it had a very nose high attitude, and was not gaining significant altitude. He could not judge the altitude, but indicated that the airplane was low. The nose dipped a little, and then went back up; however, the airplane gained little altitude. The airplane then maneuvered away from his sight and hearing.
A review of Federal Aviation Administration (FAA) airman records revealed that the 51-year-old pilot held a private pilot certificate with ratings for airplane single-engine land, single-engine sea, and instrument airplane.
The pilot held a third-class medical certificate issued on April 24, 2008. It had the limitations that the pilot must have glasses available for near vision.
An examination of the pilot's logbook indicated an estimated total flight time of 403 hours as of the last entry on July 16, 2008. He logged 19 hours in the previous 90 days, and 10 hours in the previous 30 days. He had an estimated 45 hours in this make and model, which were all in this airplane. The first flight logged in this airplane occurred on October 30, 2007.
The airplane was a Cessna A185F, serial number 18504305. The airframe logbooks noted an annual inspection on September 1, 2007, at a total time of 1,497.8 hours on the airframe and engine. The engine was a Teledyne Continental Motors IO-520-D, serial number 572938.
Fueling records at Auburn established that the airplane was last fueled on July 24, 2008, at 1338, with the addition of 46.71 gallons of 100-octane aviation fuel.
WRECKAGE AND IMPACT INFORMATION
Investigators examined the wreckage at the accident scene. The airplane came to rest inverted in a wooded area about .14 miles from the shoreline. Trees in the immediate area of the main wreckage had broken limbs and trunks. The orientation of the fuselage was 040 degrees. Fire consumed the metal skins of the cabin area, wings, front half of the floats, and parts of the empennage.
The principle impact crater (PIC) was about 7 feet long, 3 feet wide, and 8 inches deep; it ended a few feet forward of the nose of the airplane. The PIC contained one propeller blade, a float wheel, and thick plexiglass; none of these items exhibited any soot or discoloration.
Control continuity was established for the elevators, rudder, and ailerons.
MEDICAL AND PATHOLOGICAL INFORMATION
The Mason County Coroner completed an autopsy, and determined that blunt force injuries to the head and thermal injuries were the cause of death. The coroner's toxicology test detected no findings for tested drugs. It did report a 6 percent saturation of carbon monoxide. They did not post a finding on blood ethanol, and did not test urine. Toxicology tests were not performed by the Federal Aviation Administration (FAA).
TESTS AND RESEARCH
Investigators examined the wreckage at Av Tech, Maple Valley, Washington, on July 24, 2008.
Air was blown through the fuel selector valve, which was heard exiting from both the left and right fuel fittings. No obstructions were noted.
The engine was removed from the airframe for inspection and slung from a hoist in order to remove the top and bottom spark plugs. None of the spark plugs exhibited mechanical deformation, and the gaps appeared similar. All spark plug electrodes were oval and gray, which corresponded to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart. The plugs for cylinders two, four, and six had some corrosion deposits, and the top plug for number two contained debris.
The magnetos separated from the engine during the impact sequence, but were with the main wreckage. Both sustained severe thermal damage, and could not be tested.
A borescope inspection revealed no mechanical deformation on the valves, cylinder walls, or internal cylinder head.
The crankshaft would not rotate, therefore cylinders number one, three, and five were removed. The camshaft lobes appeared unremarkable. The counterweight cheeks that could be reached moved freely. The combustion deposits on the piston heads were unremarkable.
The accessory section sustained severe thermal damage. Fire consumed the fuel pump housing except for the mounting pad, and the top part of the oil pump. The oil pump drive gear was not located during the inspection. There was no metal debris noted in the oil screen. Fire consumed a portion of the oil sump; the oil pickup screen was clean and open. The oil filter was crushed, but clean.
Fire consumed the majority of the induction system including material from the throttle body, elbows, and risers. The throttle plate and linkage remained attached to the fuel control unit. The fuel control inlet screen had dark deposits. All fuel injector nozzles were clear except for number four, which had mechanical damage and debris at the outlet port. The fuel pump sustained thermal damage.
The propeller governor sustained thermal damage. The seal/screen was unrestricted.
The propeller hub remained attached to the crankshaft. The propeller hub sustained mechanical damage and one blade separated; this blade was in the principal impact crater.
The second blade bent aft at the shank in a shape similar to the outline of the cowling. It twisted toward the low pitch high revolution per minute (rpm) position. The third blade was buried in the dirt. It was severely deformed with heavy gouging and twisting.
Nahwatzel Lake is approximately 5,000 feet in length measuring from the southwest end to the northeast. The depth of the water varies depending upon the time of year. The elevation of the lake is 440 feet mean sea level.
|Narrative Type: NTSB PROBABLE CAUSE NARRATIVE
|The pilot's failure to attain and maintain adequate airspeed during initial climb, which resulted in an aerodynamic stall.